Metabolic Response to Stress, Injury or Surgery

1. Metabolic Response to Stress, Injury or Surgery

2. Objectives • The effects of trauma /Surgery on metabolism • Consequences of the metabolic response • Determination of calorie and protein requirements during metabolic stress

3. Metabolism......? • All chemical reactions involved in maintaining the living state of the cells and the organism • Metabolism is closely linked to nutrition and the availability of nutrients i.e Nutrition is the key to metabolism.Food provides a variety of substances that are essential for the building and repair of body tissues, and for the efficient functioning of the body

4. Metabolism of substrates and micronutrients is altered by trauma. • After trauma, the body’s hormonal situation changes, increasing the demand for energy, proteins and micronutrients. • If nutritional requirements are not recognized and met during starvation or trauma, there may be a loss of body mass, body protein, and impairment or loss of body functions.

6. Mediating the Response • The Endocrine System • Pituitary Gland (↑ GH, ↑ ACTH,) • Adrenal Gland (↑ Cortisol, Aldosterone) • Pancreatic (↑Glucagon,  Insulin) • Others (Renin, Angiotensin,  Sex hormones,  T4) • The net effect of the endocrine response to surgery is an increased secretion of catabolic hormones

7. Mediating the Response • Afferent Neuronal impulses from the site of injury  Hypothalamus • Efferents to sympathetic Nervous system  Adrenal Medulla↑ catecholamines (tachycardia, hypertension)

8. Mediating the Response • The endothelium, activated leucocytes and fibroblasts produce Cytokines (IL /INF) • These act on their target cells to produce different proteins

9. Mediating the Response • The Acute Inflammatory Response • Cellular activation • Inflammatory mediators (TNF, IL1, etc)

10. Consequences of the Response • Mobilization of substrates

11. Trauma/surgery causes major alterations in energy and protein metabolism. • The response to trauma can be divided into the ebb phase and the flow phase. • The ebb phase occurs immediately after trauma and lasts from 24-48 hours followed by the flow phase.After this, comes the anabolism phase and finally, the fatty-replacement phase.

12. Phases – Physiological response Injury EBB FLOW RECOVERY Days Hours Weeks ANABO LISM CATABOLISM SHOCK BUILDING UP USED ENERGY BREAKING DOWN ENERGY STORES

13. Metabolic Response to Trauma:Ebb Phase • Characterized by hypovolemic shock • Priority is to maintain life/homeostasis  Cardiac output  Oxygen consumption  Blood pressure  Tissue perfusion  Body temperature  Metabolic rate Cuthbertson DP, et al. Adv Clin Chem 1969;12:1-55Welborn MB. In: Rombeau JL, Rolandelli RH, eds. Enteral and Tube Feeding. 3rd ed. 1997

14. The ebb phase is characterized by hypovolemic shock. • Cardiac output, oxygen consumption and blood pressure all decrease, thereby reducing tissue perfusion. • These mechanisms are usually associated with hemorrhage. • Body temperature drops. • The reduction in metabolic rate may be a protective mechanism during this period of hemodynamic instability.

15. Metabolic Response to Trauma:Flow Phase •  Catecholamines •  Glucocorticoids •  Glucagon • Release of cytokines, lipid mediators • Acute phase protein production Cuthbertson DP, et al. Adv Clin Chem 1969;12:1-55Welborn MB. In: Rombeau JL, Rolandelli RH, eds. Enteral and Tube Feeding. 3rd ed. 1997

16. Key catabolic elements of flow phase • Hypermetabolism • Alterations in skeletal muscle protein • Alterations in Liver proteins • Insulin resistance

17. Metabolic Response to Trauma Fatty Acids Glucose Amino Acids Fatty Deposits Liver & Muscle (glycogen) Muscle (amino acids) Endocrine Response

18. Endocrine response in the form of increased catecholamines, glucocorticoids and glycogen, leads to mobilization of tissue energy reserves. • These calorie sources include • fatty acids and glycerol from lipid reserves, • glucose from hepatic glycogen (muscle glycogen can only provide glucose for the involved muscle) and gluconeogenic precursors (eg, amino acids) from muscle.

19. The response to trauma includes a breakdown of muscle tissue. • This mechanism provides amino acids for gluconeogenesis and for synthesis of proteins involved in immunologic response and tissue repair. • However, this process can lead to a loss of body mass, most notably body protein.

20. Prolonged metabolic stress without provision of adequate calories and protein leads to impaired body functions and ultimately malnutrition.

21. Metabolic Response to Trauma 28 24 20 16 12 8 4 0 Nitrogen Excretion (g/day) 10 20 30 40 Days Long CL, et al. JPEN 1979;3:452-456

22. Previous slide illustrates nitrogen losses in relation to trauma. • With respect to protein, the greater the trauma, the greater the effect on the nitrogen balance. • Similar to metabolic rate, patients experience nitrogen losses according to the severity and duration of the trauma.

23. Major Surgery Cirugía mayor Moderate to Severe Burn Quemadura moderada a grave Nitrogen Loss in Urine Severe Sepsis Sepsis grave Infecci Infection ó n Cirug Elective Surgery í a electiva Basal Metabolic Rate Severity of Trauma: Effects on Nitrogen Losses and Metabolic Rate Adapted from Long CL, et al. JPEN 1979;3:452-456

24. The graph illustrates that severity of injury correlates to increasing urinary nitrogen loss and increasing energy needs. • Elective surgery being least traumatic and the lowest nitrogen loss in urine, whereas burn results in an increase in basal metabolic rate and urinary loss of nitrogen.

25. Estimation of energy requirements • There are a wide variety of methods for estimating energy requirements. • Common methods include indirect calorimetry and the Harris-Benedict Equation.

26. Indirect calorimetry is based on calculating heat production by measuring oxygen consumed and carbon dioxide produced, through analysis of exhaled gas or use of pulmonary catheters.

27. The Harris-Benedict Equation calculates basal energy requirements for healthy people • It has also been applied to sick patients through the use of correction factors for stress and activity. • The simplest estimate of adequate energy intake for patients in metabolic stress is the “rule of thumb” of 25-30 kcal/kg body weight per day.

28. Determining Calorie Requirements • Indirect calorimetry • Harris-Benedict x stress factor x activity factor • 25-30 kcal/kg body weight /day

29. Metabolic Response to Starvation and Trauma: Nutritional Requirements Example: Energy requirements for patient with cancer in bed = BEE x 1.10 x 1.2 ADA: Manual Of Clinical Dietetics. 5th ed. Chicago: American Dietetic Association; 1996 Long CL, et al. JPEN 1979;3:452-456

30. Macronutrients requirements during Stress Carbohydrate • At least 100 g/day needed to prevent ketosis • Carbohydrate intake during stress should be between 30%-40% of total calories • Glucose intake should not exceed5 mg/kg/min Barton RG. Nutr Clin Pract 1994;9:127-139 ASPEN Board of Directors. JPEN 2002; 26 Suppl 1:22SA

31. Macronutrientes during Stress Fat • Should provide 20%-35% of total calories • Maximum recommendation for intravenous lipid infusion: 1.0 -1.5 g/kg/day • Monitor triglyceride level to ensure adequate lipid clearance Barton RG. Nutr Clin Pract 1994;9:127-139 ASPEN Board of Directors. JPEN 2002;26 Suppl 1:22SA

32. Macronutrientes during Stress • Dietary fat should provide between 20-35% of total calories. Maximum recommended infusion rate when administering intravenous lipids is 1.0-1.5 g/kg/day. Serum triglyceride levels in stressed patients should be monitored to ensure adequate lipid clearance.

33. Macronutrients during Stress Protein • Requirements range from 1.2-2.0 g/kg/day during stress • Comprise 20%-30% of total calories during stress Barton RG. Nutr Clin Pract 1994;9:127-139 ASPEN Board of Directors. JPEN 2002;26 Suppl 1:22SA

34. Protein requirements increase during metabolic stress and are estimated at between 1.2-2.0 g/kg/day, or approximately 20% to 30% of the total calorie intake during stress.

35. Determining Protein Requirements for Hospitalized Patients No Stress Moderate Stress Severe Stress Stress Level Calorie:Nitrogen Ratio Percent Potein / Total Calories Protein / kg Body Weight > 150:1 150-100:1 < 100:1 < 15% protein 15-20% protein > 20% protein 0.8 g/kg/day 1.0-1.2 g/kg/day 1.5-2.0 g/kg/day

36. Calorie-to-nitrogen ratios can be used to prevent lean body mass from being utilized as a source of energy. Therefore, in the non-stressed patient, less protein is necessary to maintain muscle as compared to the severely stressed patient.

37. Micronutrients • Micronutrients, trace element, vitamin, and mineral requirements of metabolically stressed patients seem to be elevated above the levels for normal healthy people. • There are no specific dosage guidelines for micronutrients and trace elements, but there are plausible theories supporting their increased intake. • The following slide lists some of these nutrients along with the rationale for their inclusion.

38. Key Vitamins and Minerals

39. Role of Glutamine in Metabolic Stress • Considered “conditionally essential” for critical patients • Depleted after trauma • Provides fuel for the cells of the immune system and GI tract • Helps maintain or restore intestinal mucosal integrity Smith RJ, et al. JPEN 1990;14(4 Suppl):94S-99S; Pastores SM, et al. Nutrition 1994;10:385-391Calder PC. Clin Nutr 1994;13:2-8; Furst P. Eur J Clin Nutr 1994;48:607-616 Standen J, Bihari D. Curr Opin Clin Nutr Metab Care 2000;3:149-157

40. Glutamine is one of the few nutrients included in the category of conditionally-essential amino acids. • Glutamine is the body’s most abundant amino acid and is involved in many physiological functions. Plasma glutamine levels decrease drastically following trauma. • It has been hypothesized that this drop occurs because glutamine is a preferred substrate for cells of the gastrointestinal cells and white blood cells. Glutamine helps maintain or restore intestinal mucosal integrity.

41. Arginine is also considered a conditionally essential amino acid.